Device for irradiating a tumor tissue

ABSTRACT

The invention relates to an apparatus and a method for irradiating tumour tissue ( 3 ) of a patient ( 10 ) by means of an ion beam ( 2 ). For that purpose, the apparatus has a deflecting device ( 1 ) for the ion beam ( 2 ) for slice-wise and area-wise scanning of the tumour tissue ( 3 ) and an ion beam energy control device for slice-wise and depth-wise scanning of the ion beam ( 2 ). An electromechanically driven ion-braking device ( 11, 12 ) is provided as a depth-wise scanning adaptation apparatus ( 5 ) for adapting the range of the ion beam ( 2 ) and has faster depth-wise adaptation than the energy control device of an accelerator. The movement of a patient is monitored by means of a movement detection device ( 7 ) for detecting a temporal and positional change in the location of the tumour tissue ( 3 ) in a treatment space ( 8 ). A control device controls the deflecting device ( 1 ) and the depth-wise adaptation apparatus ( 5 ) for adjusting the ion beam direction and ion beam range, respectively, when scanning the tumour tissue ( 3 ) in the course of temporal and positional change in the location of the tumour tissue ( 3 ) in the treatment space ( 8 ).

[0001] The invention relates to an apparatus and a method forirradiating tumour tissue of a patient by means of an ion beam, inaccordance with the independent claims.

[0002] The most recently developed ion beam scanning apparatuses andmethods, such as those on which, for example, the European PatentApplication 98 117 256.2 is based, allow increased precision in theirradiation of deep-lying tumours.

[0003] Using those apparatuses and methods, the target volume, such as atumour of a patient, is broken down into layers of identical range,which layers are then scanned area-wise in a grid pattern using an ionbeam. The ion beam is brought into a treatment space in relation to afixed coordinate system, the spatial angle of an ion beam axis in thetreatment space being fixed or emission from different spatial anglesbeing possible by means of a gantry.

[0004] In order for the tumour of a patient to be positioned in thatfixed coordinate system of the irradiation space, the patient must firstbe brought into the correct desired position relative to that coordinatesystem so that the actually irradiated or scanned volume of the ion beamconforms to the planned target volume of the tumour in the patient. Itis, moreover, necessary in the case of such known systems for thepatient to be maintained in the desired position during irradiation. Inorder to maintain the desired position, complicated devices such asindividually fabricated thermoplastic mask systems are used for fixingthe patient in position, in order to adjust the patient with millimetreaccuracy before irradiation and to stabilise the patient by means of themask during irradiation. Using the known apparatuses and methods, it isaccordingly possible only to irradiate spatially fixed target volumessuch as, for example, tumours in the head and neck region and tumoursclose to the spinal column, wherein either the head alone is fixed inposition by means of a suitable mask or a full body mask stabilises thespinal column.

[0005] Irradiation of moving target volumes, for example in the thoracicregion, has not hitherto been possible using such methods. For example,breathing movement causes the target volume to be displaced by a fewcentimetres in the thoracic region and, as a result, the desiredmillimetre precision is made impossible. It is accordingly impossible toachieve fixing in position with millimetre accuracy when, at the sametime, internal movements cause displacement of the target volume in thecentimetre range. In addition, movement of the target volume whilst beamscanning is being carried out causes substantial dose non-uniformities.

[0006] Whereas it would be possible, in the case where the ions in theion beam have constant energy, for the relatively fast, area-wise,grid-patterned scanning to follow, in terms of time, the lateralmovements of the target volume in the centimetre range, the acceleratoris not able to vary the energy sufficiently fast to follow the organmovements in terms of depth, for example as a result of breathing orheartbeat in the thoracic region of a tumour patient.

[0007] The problem of the invention is to provide an apparatus and amethod for irradiating tumour tissue of a patient by means of an ionbeam, wherein the ion beam can be adapted to spatial and temporalchange, especially spatial and temporal periodic changes in the targetvolume, both perpendicular to the beam direction and in terms of depth.

[0008] The problem is solved by the subject-matter of the independentclaims. Features of preferred embodiments are defined in the dependentclaims.

[0009] In accordance with the invention, the apparatus for irradiatingtumour tissue of a patient by means of an ion beam has a device fordeflecting the ion beam for slice-wise and area-wise scanning of thetumour tissue and has an accelerator having an ion beam energy controldevice for step-wise and depth-wise scanning of the ion beam. Inaddition, the apparatus has an ion-braking device, which is used as adepth-wise scanning adaptation apparatus for adapting the range of theion beam and which has faster depth-wise adaptation than the energycontrol device of the accelerator. Furthermore, the apparatus has amovement detection device for detecting a temporal and positional changein the location of the tumour tissue in a treatment space and has acontrol device which controls the deflecting device and the depth-wisescanning adaptation apparatus for adjustment of the ion beam directionand ion beam range, respectively, when scanning the tumour tissue in theevent of temporal and positional change in the location of the tumourtissue in the treatment space.

[0010] The apparatus according to the invention has the advantage thatmoving target volumes of a patient who is moving can be irradiated withthe same precision as non-moving target volumes in a patient who isfixed in position. For that purpose, the movement detection devicedetects the movements of the patient during irradiation, and theirradiation points are correspondingly corrected with the aid of acontrol device. In principle, it is no longer necessary, in the case ofthis apparatus, for the patient to be initially adjusted with millimetreaccuracy in the fixed spatial coordinates because, with the aid of themovement detection device, the actual initial location of a patient canalso be adapted to the treatment program and/or the treatment programcorrected accordingly.

[0011] In a preferred embodiment of the invention, the apparatus has twoelectromagnets, by means of which the deflecting apparatus makespossible area-wise scanning. The electromagnets deflect the ion beamorthogonally to the ion beam axis in an X direction and a Y direction,which are, in turn, perpendicular to one another, in order to providearea-wise scanning of the tumour tissue which, relative to depth-wisescanning by means of the ion beam energy control device, is fast. Forthat purpose, the electromagnets are controlled by fast-reacting powerunits and measurement devices. Those devices can accordingly also beused to carry out correction and adaptation when scanning tumour tissuein the case of temporal and positional change in the location of thetumour tissue in the treatment space orthogonally to the ion beam axis.

[0012] In a preferred embodiment of the invention, the apparatus has atleast one accelerator, by means of which the energy of the ion beam isadjustable so that the tumour tissue can be irradiated slice-wise,staggered in terms of depth. That is associated with the advantage thatthe entire tumour tissue can be successively scanned slice-wise, therange of the ion beam being adjustable from slice to slice by modifyingthe energy of the ion beam. For that purpose, the accelerator consistsessentially of a synchrotron or a synchrocyclotron, in which ions ofequal mass and equal energy can be accelerated step-wise to higherenergies. Because of the complexity of the control functions for theaccelerator, the energy of the ion beam cannot be adapted to specifiedranges within the irradiation space or within the tumour volumesufficiently quickly or with the requisite precision for it to bepossible to follow the movements of the tumour tissue, or patient,automatically.

[0013] In a preferred embodiment of the invention, the depth-wisescanning adaptation apparatus therefore has two ion-braking plates ofwedge-shaped cross-section, which cover the entire irradiation field ofthe ion beam and allow fast depth-wise scanning adaptation in the caseof moving tumour tissue.

[0014] For that purpose, in a preferred embodiment of the invention, theion-braking plates are arranged on electromagnetically actuatablecarriages. With the aid of those electromagnetically actuatablecarriages, the position of the wedge-shaped ion-braking plates can bechanged within milliseconds and, accordingly, the length of the brakingpath of the ions provided in an overlap region of the wedge-shapedbraking plates can be varied by the ion-braking plates. For thatpurpose, the ion-braking plates overlap in the entire irradiation fieldof the ion beam and can accordingly adapt the ions in terms of theirrange, irrespective of their position, to positional and temporalchanges in a moving target volume.

[0015] In a preferred embodiment of the invention, the ion-brakingplates are mounted on linear motors. Such linear motors have theadvantage that continuous, fine regulation of ion braking is possiblefor adaptation of depth-wise scanning of the target volume. Changing theposition of the wedge-shaped ion-braking plates with the aid of linearmotors is, moreover, not only extremely precise positionally but is alsoadaptable with extreme speed of reaction to temporal change in thetarget volume in terms of depth.

[0016] In a further embodiment, a water-filled cylinder of variablethickness is used instead of the wedges. The covers of the cylinder aremade from transparent plates, for example from two plexiglass or silicaglass panes, the upper pane of which is moved by 2 or 4 high-performancelinear motors. The side covering of the cylinder is in the form of abellows made from steel or rubber. Variation of the thickness of thewater layer is assisted by a hydraulic system which, when the cylinderis drawn apart, pumps water into the cylinder and, when it is pressedtogether, draws water out so that the drive is spared and the formationof vacuoles is prevented.

[0017] This embodiment has the advantage that a smaller minimumthickness is possible than in the case of the wedges. In the case of thewedges, the minimum thickness is calculated from the wedge slope×fieldsize (typically 5 cm). In the case of the cylinder arrangement, theminimum thickness is given by the thickness of the two covers (typically1 cm). That small minimum thickness reduces the beam scatter andaccordingly improves the beam quality. The cylinder arrangement is,moreover, more compact than the wedge construction in the transversedirection.

[0018] In a further preferred embodiment of the invention, the movementdetection device has at least two measurement sensors which, from twospatial angles in relation to an ion beam axis, detect the temporal andpositional location of markings on a region of the body of a patientcontaining tumour tissue. Such markings can be applied usingskin-compatible luminous colours in the form of dots, dashes or othergeometric shapes or in the form of luminous elements so that they can beclearly detected and measured by the measurement sensors.

[0019] In a further preferred embodiment of the invention, themeasurement sensors are precision video cameras, which co-operate withan image-evaluating unit. By that means it is advantageously possiblefor the movements of a region of the body in the vicinity of tumourtissue to be exactly measured and correlated to the temporal andpositional changes in the location of the tumour tissue.

[0020] Alternatively to the movement detection system which usesmarkings on the surface of the body and a precision video camera, afurther embodiment of the invention has an X-ray system, which detectsthe movements of the tumour tissue directly in the body. In the case ofthat movement detection system, two X-ray tubes are mounted with theirbeam directions orthogonal to the ion beam. The two X-ray tubes are, inturn, also oriented perpendicular to one another. In addition, twosensitive X-ray image intensifiers are in each case mounted opposite, onthe other side of the patient. The X-ray tubes emit short X-ray flashesof low power, in order to keep the dosage low, at a frequency of, forexample, 20 Hz. The associated X-ray images are recorded by the imageintensifiers and digitised. As a result, an image sequence for twodirections is obtained, from which, using a suitable method andappropriate software, the displacement of the target points P₁ isdetermined in virtually real time with a delay of approximately 50 ms.

[0021] That embodiment has the advantage that much more information onmovements in the interior of the body is obtained from the X-rayrecordings than from external markings on the surface of the body,allowing more precise determination of temporal and positional organdisplacements.

[0022] In principle, irradiation of the tumour volume is made up fromimage points, which are set beside one another area-wise in a gridpattern in the form of a slice, the ion beam being deflected fromscanning point to scanning point orthogonally to its beam axis in an Xdirection and a Y direction. Even though the energy of the ions in anion beam can be kept constant by the accelerator in question, the numberof ions per volume point is not constant over time. In order,nevertheless, to beam an ion beam dose of equal magnitude into everyvolume point of the tumour tissue, an ionisation chamber having a fastread-out for monitoring the intensity of the ion beam flow is, in apreferred embodiment of the invention, arranged as a transmissioncounter in the beam path of the ion beam. Such a transmission counterdetermines the dwell time of the ion beam at a volume point beingirradiated in the tumour volume, and a control unit connected theretodiverts the ion beam to the next volume point as soon as a specifiedbeam dose has been achieved. It is, consequently, advantageouslypossible to scan a volume slice of a tumour volume area-wise in a gridpattern.

[0023] The ionisation chamber is preferably arranged between thedeflecting device and the depth-wise scanning adaptation apparatus,especially as the depth-wise scanning adaptation apparatus having itswedge-shaped braking plates or the water layer between transparentplates merely controls the ions in terms of their range without,however, influencing the ion dose.

[0024] A method of irradiating tumour tissue of a patient by means of anion beam comprises the following method steps:

[0025] placing the patient on an apparatus matched to the contour of thepatient for the purpose of positioning the patient in an irradiationspace,

[0026] applying markings to a region of the body of the patient, closeto the tumour tissue,

[0027] determining the temporal and positional change in the markings bymeans of a movement detection device or capturing X-ray images of thetumour tissue from two mutually perpendicular directions of X-ray beamsorthogonal to the ion beam,

[0028] adjusting the ion beam, whilst scanning the tumour tissue usingan ion beam deflecting device and an ion beam energy control device, bymeans of an additional depth-wise scanning adaptation apparatus, whichadapts the range of the ion beam to the temporal and positional changesin the markings, determined by the movement detection device, inco-operation with the ion beam deflecting device.

[0029] Using that method, it advantageously becomes possible to achievethe same precision in the millimetre range when irradiating movingtumour volumes in a patient who is moving as in the case of the patientwho is fixed in position, even when the tumour tissue moves up toseveral centimetres periodically, for example as a result of heartbeator breathing air. In this method, ion beam irradiation continuouslyfollows the temporal and positional change in the location of the tumourtissue and it is not necessary to delay the irradiation until arepeating positional location has been achieved. Slow movements of thepatient that occur on a non-periodic basis are also allowable and ionirradiation thereof can, with the aid of the depth-. wise adaptationapparatus and the deflecting device, be adapted temporally andpositionally. Only in the case of sudden changes in location such asfits of coughing does the irradiation procedure have to be suspended.

[0030] Compared to methods that allow irradiation only when identicallocations of the tumour tissue have been achieved, the method accordingto the invention has the advantage that the irradiation time for apatient can be significantly shortened because the irradiation procedureis not dependent on, for example, the periodicity of the heartbeat or ofthe breathing of a patient.

[0031] Further advantages and features of the present invention will bedescribed below in further detail with respect to embodiments withreference to the accompanying drawings.

[0032]FIG. 1 is a representation, in diagrammatic form, of an embodimentof the invention in the course of irradiating tumour tissue in thethoracic region of a patient.

[0033]FIG. 2 is a representation, in diagrammatic form, of an embodimentof a movement detection device.

[0034]FIG. 3 shows a comparison between neighbouring volume scanningpoints in the case of a positionally and temporally fixed and,consequently, static, target volume and a positionally and temporallymoving and, consequently, dynamic, target volume.

[0035]FIG. 4 is a representation, in diagrammatic form, of an embodimentof the invention in the course of irradiating tumour tissue in the headregion of a patient.

[0036]FIG. 5 is a representation, in diagrammatic form, of anion-braking device by means of a variable water volume.

[0037]FIG. 6 is a representation, in diagrammatic form, of a furtherembodiment of the invention in the course of irradiating the tumourtissue in the head region of a patient.

[0038]FIG. 1 is a representation, in diagrammatic form, of an embodimentof the invention in the course of irradiating tumour tissue 3 in thethoracic region 23 of a patient 10. For that purpose, the apparatus hasan ion beam 2, which is deflected from its ion beam axis 15 by means ofan ion beam deflecting device 1 orthogonally to the ion beam axis 15,more specifically in an X direction on passing through a gap 24 in anelectromagnet 13 and in a Y direction on passing through a gap 25 in anelectromagnet 14, the gaps being arranged perpendicular to one another.

[0039] Before impinging upon the tumour tissue 3 of a patient, the ionbeam further passes through an ion-braking device 11, 12,electromagnetically driven in arrow direction R, which is used as adepth-wise scanning adaptation apparatus 5 for adapting the range of theion beam 2 and which has faster depth-wise adaptation than an energycontrol device (not shown), by means of which the energy of the ion beamis controlled before entering the gaps 24, 25 in the electromagnets 13and 14.

[0040] The ion beam energy control device (not shown) brings aboutstaggered depth-wise scanning of the tumour tissue 3; as a result ofincreasing the energy in step-wise manner after each slice-wise andarea-wise scan the ion beam penetrates deeper into the tumour tissue sothat, in the end, the entire tumour tissue is destroyed as a result ofslice-wise and depth-wise scanning of the ion beam.

[0041] On movement of the patient 10 depicted in this instance into aposition shown by a broken line, the location of the tumour tissue 3 isalso displaced so that in the case of static irradiation, which isunable to follow the movement of the patient, healthy tissue would beirradiated and destroyed.

[0042] In order to avoid that, the apparatus in FIG. 1 has a movementdetection device 7 for detecting a temporal and positional change in thelocation of the tumour tissue 3 in a treatment space 8. That movementdetection device 7, which in this embodiment of the invention consistsof two precision video cameras 21 and 22, follows the movement ofmarkings on a region of the body of the patient 10 and is communicationwith an image-evaluating device, which correlates the detected changedvalues of the markings with the temporal and positional change in thelocation of the tumour tissue 3.

[0043] A control device (not shown in FIG. 1) controls both thedeflecting device 1 having the two electromagnets 13 and 14 and thedepth-wise scanning adaptation apparatus having the ion-braking device11, 12 for adjusting, on the one hand, the ion beam direction and, onthe other hand, the ion beam range when scanning the tumour tissue inthe case of temporal and positional change in the location of the tumourtissue 3 in the treatment space 8. Using the apparatus shown in FIG. 1,greater precision of beam application and, consequently, improvedclinical success are achieved in the more than 100-year history of thedevelopment of beam therapy.

[0044] The continued increase in precision has resulted in the use ofthis scanning system comprising two electromagnets arrangedperpendicular to one another, through the gaps of which magnets an ionbeam is guided and deflected. When the apparatus according to FIG. 1 isused, the target volume, namely the tumour tissue 3, is scanned with afine beam of ions at variable intensity. The diameter of that ion beamis in the millimetre range and the precision with which the targetvolume can be subjected to an ion dose is likewise in the range of a fewmillimetres.

[0045] In the event of displacement of the target volume 26 duringirradiation, there arises a discrepancy between the actual beam focusand the actual target point and, consequently, incorrect irradiationinside the target volume 26, which is associated with local under-dosageor over-dosage. Scanning methods without the apparatus of the inventionaccording to FIG. 1 cannot, therefore, be used currently in the case ofmoving target volumes 26.

[0046] Other irradiation apparatuses operate with a highly opened-outbeam bundle and with a likewise very highly spread-out dose maximum interms of depth. Such opened-out beam bundles can cover the entire targetvolume without area-wise and slice-wise scanning and, by virtue of thelarge irradiation field, they do not produce dosage non-uniformitiesinside the target volume as would be the case if slice-wise scanningapparatuses were to be used in the case of a moving target volume. Inthe case of apparatuses having an opened-out beam bundle, the movementof organs has an effect only at the edge and can therefore becompensated by enlarging the irradiation volume so that moving parts ofthe target no longer leave the irradiation volume. However, that means,conversely, that a large region of normal healthy tissue at the edge ofthe target volume also has to be irradiated so that, using an opened-outbeam bundle whilst there is at the same time movement of the irradiatedbody, reduced precision and at the same time increased negativeside-effects are the consequence for the patient.

[0047] Using an apparatus as shown in FIG. 1, but without a depth-wisescanning adaptation apparatus 5, organ movements can be taken intoaccount only if the cross-section of the ion beam 2 is madesubstantially larger. Such a solution means, however, that precision inthe lateral region is likewise reduced, and in the longitudinal doseprofile no correction is made because, with beam opening-out, themovement in the beam direction cannot be corrected. Consequently, ifopening-out of the beam is used for covering organ movements, the resultis still non-uniform dosage distribution in the internal target volumein the beam direction.

[0048] A further possibility for using the apparatus according to FIG. 1without a depth-wise scanning adaptation apparatus 5 and neverthelesstaking organ movements into account can comprise detecting periodicmovements of, for example, the thoracic region of a patient with the aidof the movement detection device 7 and carrying out irradiation onlywhen the thorax assumes identical positions. Such an apparatus, whereinno depth-wise scanning adaptation apparatus is provided but wherein theperiodic movement of the thorax of a patient is detected, would increasethe irradiation and treatment time for a patient many times because, foreach volume point in the slice-wise scanning of the tumour volume, it isnecessary first to wait for the tumour to be in an identical position.Only opening-out of the beam can reduce the treatment time to realisticvalues in this instance, which is, in turn, as mentioned above,associated with a loss of precision.

[0049] Consequently, the apparatus according to the invention proves tobe the approach by means of which the depth of penetration of the ionbeam can be optimally adapted to the organ movements of a patient sothat tumour tissue can be very precisely irradiated with millimetreaccuracy in the event of temporal and positional change in location.

[0050]FIG. 2 is a representation, in diagrammatic form, of an embodimentof a movement detection device 7. This embodiment ascertains themovement of a region of the body of a patient 10 by means of twoprecision video cameras 21 and 22, which detect markings 4 on the thoraxof a patient 10 from two different spatial angles, α and β, and sendthem to an image-evaluating unit (not shown). The markings 4 are soselected that, on the one hand, they are arranged in the vicinity of thetumour tissue to be irradiated and, on the other hand, accuratelycapture the thorax movements so that it is possible to deduce, from thetemporal and positional changes in the markings 4, the temporal andpositional displacements of location of the tumour tissue.

[0051] In the Cartesian coordinate system of the irradiation space 8having the coordinate directions X, Y and Z, the spatial angles α and βhave spatial angle components α_(x), α_(y) and α_(z) for the spatialangle α and β_(x), β_(y), and β_(z) for the spatial angle β. The spatialangles α and β are, by means of those components, clearly correlated tothe coordinate system X, Y and Z in the irradiation space 8.

[0052] The position of a first precision video camera 21 in thatarrangement has the projection points A_(α), B_(α) and C_(α), theprojection point A_(α) passing through the plane generated by thecoordinates X and Z, the projection point B_(α) passing through theplane generated by the coordinates Y and X and the projection pointC_(α) passing through the plane generated by the coordinates Z and Y.The position of the second camera 22 has the projection points A₆₂ , B₆₂and C₆₂ , the projection point A₆₂ passing through the plane generatedby the coordinates X and Z, the projection point B₆₂ passing through theplane generated by the coordinates Y and X and the projection point C₆₂passing through the plane generated by the coordinates Z and Y. By wayof those projection points, the position of the precision cameras 21 and22 is likewise clearly defined in the irradiation space 8, thecoordinates of the spatial angle α of the first precision video camera21 being x_(α), y_(α) and z_(α) and the coordinates of the spatial angleβ in the case of the position of the second precision video camera 1being x_(β), y_(β) and z_(β).

[0053] The largest organ movements and, consequently, the largesttemporal and positional changes in the marking 4 occur in the lungregion of a patient during breathing. In the central thoracic region 23,displacements having an amplitude of up to 1 cm and, at the edge of thelungs, up to 3 cm are found. As a result of breathing, thosedisplacements are periodic. The displacement of the internal structuresis correlated to the movements of the body surface. Optical monitoringand detection of the body surface by means of the precision videocameras 21 and 22 therefore supplies respective actual locationcoordinates for the internal structures. For that purpose, markings 4 inthe form of coloured dashes, coloured dots or luminous elements such aslight-emitting diodes can be applied to the body surface. As a result,it is advantageously possible, without invasive intervention, to capturethe internal geometry of the patient at any point in time, and also thetemporal course of the displacements of the internal structures and thespeed of the movements in question.

[0054]FIG. 3 shows a comparison between neighbouring volume scanningpoints P_(i) and P_(i+1) and P′_(i+1) in the case of a positionally andtemporally fixed, and consequently static, target volume V_(s) and apositionally and temporally moving, and consequently dynamic, targetvolume V_(d). The determination of the movement of the internalstructures in correlation to the surface must be known beforeirradiation. That can be determined from model calculations or also frommeasurements.

[0055] Starting from a momentary recording at time-point t=0, it ispossible, in the case of a short-time recording in a manner similar tothe case of the grid scanning method for a non-moving object, for thetarget volume to be broken down into layers having a depth coordinatez_(i) of equal particle range and each layer having a lateral network inthe X and Y direction having reference image points, which cover volumescanning points P_(i) (x_(i), y_(i), z_(i)). During irradiation, thoseimage points are, by virtue of the movement, displaced to a positionP′_(i)(x_(i)+Δx_(i)(t)y_(i)+Δy_(i)(t)z_(i)+Δz_(i)(t)). The discrepanciesor displacements Δx, Δy and Δz result from the three-dimensional speeddistribution of organ movement over time Δt, which is necessary for doseapplication at a volume point P of the tumour tissue 3. For example, amaximum displacement of the thoracic region 23 of 3 cm and a breathfrequency of about 0.5 Hz, that is to say a duration of 2 s, results ina speed for the organ movements of about v_(organ)=3 cm/s.

[0056] The image points P_(i), which then become volume scanning points,are, in the case of a lateral and longitudinal scanning procedure,spaced from 1 to 3 mm apart, that is to say after an irradiation dose atpoint P_(i) the next neighbouring point at a distance of from 1 to 3 mmP_(i+1) is accessed and a beam dose is again introduced at that volumescanning point. The time for application of the dose in a volumescanning point P_(i) or P_(i+1) is less than 10 ms. Consequently, thetarget point moves a maximum of 0.3 mm in that 10 ms, that is to sayvery much less than the spacing between two volume scanning points P_(i)and P_(i+1). Because the movement in the volume scanning point P_(i)currently being irradiated is, during irradiation, less than the lack ofsharpness of the irradiation, it is not necessary for the point P_(i) tobe displaced during its irradiation. After P_(i) has been irradiated,the beam has to pass on to a point P′_(i+1), which has been moved fromthe originally planned point P_(i+1) in accordance with the coordinatemovement of the organ. That organ movement is designated r in FIG. 3 andresults from the speed, r=v_(organ)·Δt. The actual position of the(i+1)th point is:

P′_(i+1)=(x_(i+1)+Δx_(i+1)(t),y_(i+1)+Δy_(i+1)(t),z_(i+1)+Δz_(i+1)(t))

[0057] The discrepancy or displacement of the moving points P′_(i) fromthe originally static network of volume scanning points P_(i) resultsfrom the displacement during the irradiation time. In the case of theusual cyclical and periodic movements such as breathing, heart rate etc.those points likewise follow a cyclic curve, which can be correlated tothe movement of the body surface. Parameterising of the path over timeis therefore possible. Using the apparatus according to the inventionand the method according to the invention for irradiating tumour tissueof a patient by means of an ion beam, non-cyclic processes can becontrolled only if the movement process does not occur suddenly butrather at a speed that is substantially slower than the scanning speedof the ion beam. In the event of sudden, hurried movements such as thoseoccurring, for example, in the case of a coughing fit, the apparatusmust be capable of being shut down at short notice in order to protecthealthy tissue from receiving a dose in error.

[0058]FIG. 4 is a representation, in diagrammatic form, of an embodimentof the invention in the course of irradiating tumour tissue 3 in thehead region 6 of a patient 10. The apparatus of FIG. 4 correspondsessentially to the apparatus according to FIG. 1 and likewise has twoelectromagnets 13 and 14 for deflecting the ion beam 2 from its axialdirection 15, the range of the ion beam being controlled by ion-brakingplates 16 and 17, which are wedge-shaped in profile. The overlappingregions 28 and 29 cover at least the entire irradiation region; bymoving the wedge-shaped profiles of the braking plates 16 and 17 towardsone another, the ion beam 2 braking path through the braking plates 16and 17 is increased and, consequently, the range of the ion beam isreduced. By moving the wedge-shaped braking plates away from oneanother, the braking path is reduced and, consequently, the range of theion beam is increased.

[0059] The direction of movement of the wedge-shaped braking plates 16and 17 is indicated by the arrows R in FIG. 4. The displaceable brakingplates having a wedge-shaped profile are, in this embodiment, driven bya high-performance linear motor so that beam-intensive controlleddepth-wise adaptation can be accomplished. For the linear drive, thedepth-wise scanning adaptation apparatus 5 has an electronic controlsystem which co-operates with the movement detection device 7 and thedeflecting device 1. In order to ensure fast reaction, the armatures ofthe linear motor, which carries the braking plates 16 and 17 on acarriage, are air-mounted and the motor currents of the linear motor arecontrolled by means of a servo motor control.

[0060]FIG. 5 is a representation, in diagrammatic form, of anion-braking device 43 by means of a variable water volume. Componentshaving identical functions to those in the preceding Figures areidentified by identical reference symbols and are not separatelydescribed.

[0061] Reference symbol 44 denotes a layer of water, which is enclosedbetween two transparent plates 31 and 32. Of the transparent plates 31,32, the plate 31 can be moved by means of linear motors 34 and 35. Thenumber of linear motors can be increased as desired in order to increasethe speed of displacement of the plate 31. The water layer 44 issafeguarded against outflow laterally by means of bellows 37. In orderto take up the water volume or to add water, depending upon thedirection of movement in arrow directions G and F, a compensating tank36 is provided, which hydraulically assists the linear motors 34 and 35by pumping in water when the water layer 44 is being increased and bydrawing water off when the thickness of the water layer 44 is beingreduced. Reference symbol 33 denotes the intermediate space filled withwater. The ion beam 2 is passed through the water layer 44 for thepurpose of braking and, in so doing, must also penetrate through thetransparent plates 31 and 32, which can be made from glass orplexiglass. The smallest braking is achieved when the two plates 31 and32 abut one another. They then also have an extremely small thickness,which minimises the scatter of the ion beam.

[0062]FIG. 6 is a representation, in diagrammatic form, of a furtherembodiment of the invention in the course of irradiating tumour tissue 3in the head region of a patient. Components having identical functionsto those in the preceding Figures are identified by identical referencesymbols and are not separately described.

[0063] This further embodiment differs from the embodiment according toFIG. 4 in that the wedge system is not used as the ion-braking device 43but rather the braking device 43 shown in FIG. 5 is used. The furtherembodiment in FIG. 6 also differs from the embodiments in FIG. 1 andFIG. 4 in that a system comprising at least two X-ray tubes is used asthe movement detection system. The measurement sensors 19 and 20 areX-ray tubes, which direct X-ray beams 38 and 39, at a right angle-to oneanother, at the tumour tissue 3 of the patient 10. Those X-ray beams aredirected at the tumour tissue by X-ray flashes of low power at afrequency of, for example, 20 Hz and are received by corresponding imageintensifier plates or sensor plates 40 and 41, which pass their signalson to the evaluating device 42. That movement detection system usingX-ray beams is capable of directly following the movements of the tumourvolume inside the body and, consequently, of controlling the brakingdevice 43 very precisely.

FIRST EXAMPLE OF IMPLEMENTATION OF THE METHOD

[0064] In a first Example of implementation of the method, beforeirradiation, the surface of the patient is provided with significantmarkings such as, for example, coloured markings on the skin orlight-emitting diodes etc. The patient is placed, for example, on a foambed, as can be seen in FIG. 1 and FIG. 4 having reference numeral 30,which is adapted to his body. By that means, a positioning accuracy ofabout 1 cm can be achieved without constraint. In the irradiationposition, as shown in the Figures FIG. 1 and FIG. 4, the patient 10 ismonitored by a precision video system of at least two precision videocameras 21 and 22 from different spatial directions at spatial angles αand β, which record the position of the markings 4 (cf. FIG. 2) as afunction of time and produce a time-dependent correction function forthe image points or volume scanning points P_(i)′(t).

[0065] In order to achieve fast displacement of the ion beam 2 in threedimensions, the lateral intensity-controlled grid scanner comprising twoelectromagnets 13 and 14 is combined with a depth-wise scanningadaptation apparatus 5, because in no ion accelerator is it possible foran ion beam energy control device to carry out fast energy variationduring irradiation of a volume point P. The lateral scanning part, whichas mentioned above comprises two electromagnets, whose deflectiondirections are arranged perpendicular to one another and to the beamaxis 15, is controlled by fast power units so that rapid lateralscanning adaptation in the X and Y directions is ensured.

[0066] In addition to the scanning device 1 in the X and Y directions,there is arranged directly in front of the patient anelectromechanically operated depth-wise scanning adaptation apparatuscomprising essentially two wedges, which are mounted, working inopposite directions, on a linear motor and which cover the entireirradiation field. That depth-wise scanning adaptation apparatus servesonly for correction of the depth-wise positional change in the imagepoints caused by movement of the patient or of the patient's organs.That depth-wise scanning adaptation apparatus does not need to cover theentire depth of the target volume.

[0067] For coarse depth-wise variation, the energy variation of asynchrotron or other accelerator is used. In that process, the beam flowis monitored by means of an ionisation chamber installed in the beampath in front of the patient and is switched from a volume scanningpoint P_(i) to the next scanning point P_(i+1) when the necessaryparticle dose per volume scanning point P has been achieved. At the sametime, in accordance with the precision video camera monitoring of thepatient, the surface movement is measured, from which the movement ofthe internal structures in the target volume is calculated.

[0068] The magnetic values of the deflecting magnets and the depth-wiseadaptation values of the wedge-shaped braking plates are corrected onthe basis of the movement of the target points in three dimensions. Thefact that the beam in this kind of method and apparatus is notinterrupted during irradiation also means that there are nonon-irradiated locations in the tumour tissue. The precision in theinterior and also the sharp edge fall-off of static irradiation isconsequently also achieved for moving organs with dynamic irradiation.

[0069] In addition, the apparatus and the method are invariable alsowith respect to compression of volume doses. In the case of volumecompression, for example in the lungs, the image points come to liecloser together. As a result, the local particle fluence is increased.At the same time, the mass density is also increased as a result of thecompression. Because the dose is defined as the energy deposition overdensity, it is unaffected by compression to a first approximation. Thatmeans that the particle movement of the individual beam positions doesnot need to be corrected during irradiation in the case of the apparatusaccording to the invention and the method according to the invention.

SECOND EXAMPLE OF IMPLEMENTATION OF THE METHOD

[0070] In a second Example of implementation of the method, instead ofthe marking on the body of the patient, the temporal and positionalchanges in the tumour tissue are ascertained directly by means of X-raybeams. For that purpose, after orientation of the patient, two X-raybeams are directed at the tumour tissue, which are arrangedperpendicular to the ion beam 2 and which supply short X-ray flashes atlow power in order to keep low the dose to which the patient issubjected. Those flashes can be directed at the tumour tissue at afrequency of 20 Hz. The X-ray beam directions are offset from another at90° and together are arranged orthogonally with respect to the ion beam2. By means of the X-ray beam flashes, image intensifier plates areilluminated, which pass their signals to an evaluating unit 42, whichcontrols the braking device 43. The braking device 43 in this secondExample of implementation of the invention is a water layer 33, thethickness of which is varied and which is arranged between twotransparent plates 31 and 32. Fast variation of the water layerthickness is effected by modifying the intermediate space 33 between thetwo transparent plates 31 and 32. That displacement is carried out bylinear motors 34 and 35, a compensating vessel 36 at the same timeproviding for pressure compensation and volume compensation of thewater. All other irradiation steps for treating the tumour volumecorrespond to the method steps already described in the first Example ofimplementation.

LIST OF REFERNCE SYMBOLS

[0071]1 ion beam deflecting device

[0072]2 ion beam

[0073]3 tumour tissue

[0074]4 marking

[0075]5 depth-wise scanning adaptation apparatus

[0076]6 head region

[0077]7 movement detection device

[0078]8 treatment room

[0079]9 ion beam energy control device

[0080]10 patient

[0081]11, 12 ion-braking device

[0082]13 electromagnet for X deflection

[0083]14 electromagnet for Y deflection

[0084]15 ion beam axis

[0085]16, 17 ion-braking plates

[0086]19, 20 two measurement sensors

[0087]21, 22 two precision video cameras

[0088]23 thoracic region

[0089]24 gap in the electromagnet 13

[0090]25 gap in the electromagnet 14

[0091]26 target volume

[0092]27 edge of the lungs

[0093]28, 29 overlapping regions

[0094]30 foam bed

[0095]31, 32 transparent plates

[0096]33 intermediate space

[0097]34, 35 linear motors

[0098]36 compensation tank

[0099]37 bellows

[0100]38, 39 X-ray beams

[0101]40, 41 sensor plates

[0102]42 evaluating unit

[0103]43 ion-braking device

[0104]44 water layer

[0105] V_(s) static target volume

[0106] V_(d) dynamic target volume

[0107] P, P_(i) volume scanning point

[0108] P_(i+1) volume scanning point adjacent to P_(i)

[0109] α, β spatial angles

[0110] α_(x), α_(y), α_(z) components of spatial angle α

[0111] β_(x), β_(y), β_(z) components of spatial angle β

[0112] x_(α), y_(α), z_(α) coordinates of the spatial angle α at thefirst camera position

[0113] y_(β), y_(β), z_(β) coordinates of the spatial angle β at thesecond camera position

[0114] A_(α), B_(α), C_(α) projection points onto the planes XZ (A_(α));YX(B_(α)); ZY(C_(α)) of the first camera position

[0115] A_(β), B_(β), C_(β) projection points onto the planes XZ (A_(β));YX(B_(β)); ZY(C_(β)) of the second camera position

1. Apparatus for irradiating tumour tissue (3) of a patient (10) bymeans of an ion beam (2), having a deflecting device (1) for the ionbeam (2) for slice-wise and area-wise scanning of the tumour tissue (3)and an accelerator having an ion beam energy control device forstep-wise and depth-wise scanning of the tumour tissue (3),characterised in that the apparatus further has: an electromechanicallydriven ion-braking device (11, 12), which is used as a depth-wisescanning adaptation apparatus (5) for adapting the range of the ion beam(2) and which has faster depth-wise adaptation than the energy controldevice of the accelerator, a movement detection device (7) for detectinga temporal and positional change in the location of the tumour tissue(3) in a treatment space (8), and a control device which controls thedeflecting device (1) and the depth-wise scanning adaptation apparatus(5) for adjusting the ion beam direction and the ion beam range,respectively, when scanning the tumour tissue (3) in the course oftemporal and positional change in the location of the tumour tissue (3)in the treatment space (8).
 2. Apparatus according to claim 1,characterised in that the deflecting device (1) has two electromagnets(13, 14), which, for slice-wise and area-wise scanning of the tumourtissue (3), deflect an ion beam orthogonally to the ion beam axis (15)in an X direction and a Y direction, which are in turn locatedperpendicular to one another.
 3. Apparatus according to claim 2,characterised in that the electromagnets are controlled by fast-reactingpower units.
 4. Apparatus according to one of the preceding claims,characterised in that the apparatus has accelerators by means of whichthe energy of the ion beam (2) is arranged to be so adjusted that thetumour tissue (3) can be irradiated slice-wise, staggered in terms ofdepth.
 5. Apparatus according to one of the preceding claims,characterised in that the depth-wise scanning adaptation apparatus (5)has, for fast depth-wise scanning adaptation in the case of movingtumour tissue (3), an electromechanically operated ion-braking devicewhich has two ion-braking plates (16, 17), which in cross-section arewedge-shaped and which cover the entire irradiation field of the ionbeam (2).
 6. Apparatus according to claim 5, characterised in that theion-braking plates (16, 17) are mounted on linear motors.
 7. Apparatusaccording to claim 5, characterised in that the ion-braking plates (16,17) are arranged on electromagnetically actuatable carriages. 8.Apparatus according to one of claims 5 to 7, characterised in that theion-braking plates are arranged to be displaced in opposite directions,their wedge-shaped cross-sections overlapping in the region of the ionbeam (2).
 9. Apparatus according to one of claims 1 to 4, characterisedin that the depth-wise scanning adaptation apparatus (5) has, for fastdepth-wise scanning adaptation in the case of moving tumour tissue (3),a hydraulically assisted ion-braking device wherein the thickness of awater layer (30) between two transparent plates (31, 32), through whichthe ion beam (2) is directed, is adapted to the movements of the tumourtissue.
 10. Apparatus according to claim 9, characterised in that thetwo transparent plates (31, 32) are arranged to be moved towards oneanother and have water in their intermediate space (33).
 11. Apparatusaccording to claim 9 or 10, characterised in that the spacing betweenthe transparent plates (31, 32) and, consequently, the thickness of thewater layer (33) are arranged to be adjusted by means of linear motors(34, 35).
 12. Apparatus according to one of claims 9 to 11,characterised in that the depth-wise scanning adaptation apparatus (5)has a hydraulically operated compensation tank (36) for the water volumebetween the transparent plates (31, 32).
 13. Apparatus according to oneof claims 9 to 12, characterised in that a bellows (37) is arrangedbetween the transparent plates (31, 32).
 14. Apparatus according to oneof the preceding claims, characterised in that the movement detectiondevice (7) has at least two measurement sensors (19, 20), which detect,from two spatial angles (α, β) in relation to an ion beam axis (15), thetemporal and positional location of markings on a region of the body ofa patient (10) that contains tumour tissue(3).
 15. Apparatus accordingto claim 14, characterised in that the measurement sensors (19, 20) areprecision video cameras (21, 22), which cooperate with animage-evaluating unit.
 16. Apparatus according to one of claims 1 to 13,characterised in that the movement detection device (7) has at least twomeasurement sensors (19, 20), which are arranged orthogonally to ionbeam and perpendicular to one another, the temporal and positionalchange in the location of the tumour tissue being monitored by shortpulses of X-ray beams (38, 39), and the movement detection device (7)having, for detection of the images of the tumour tissue,correspondingly arranged sensor plates (40, 41) and an evaluating unit(42).
 17. Apparatus according to one of the preceding claims,characterised in that an ionisation chamber having a fast read-out formonitoring the intensity of the ion beam flow is arranged as atransmission counter in the beam path of the ion beam (2).
 18. Apparatusaccording to claim 17, characterised in that the ionisation chamber isarranged between the deflecting device (1) and the depth-wise scanningadaptation apparatus (5).
 19. Method of irradiating tumour tissue of apatient by means of an ion beam (2), which method comprises thefollowing method steps: placing the patient (10) on an apparatus matchedto the contour of the patient for positioning the patient (10) in anirradiation space (8), applying markings to a region of the body of thepatient (10), close to the tumour tissue (3), determining the temporaland positional change in the markings by means of a movement detectiondevice (7) or capturing X-ray images of the tumour tissue from twomutually perpendicular directions of X-ray beams orthogonal to the ionbeam, adjusting the ion beam (2), whilst scanning the tumour tissueusing an ion beam deflecting device (1) and an ion beam energy controldevice, by means of an additional depth-wise scanning adaptationapparatus (5), which adapts the range of the ion beam to the temporaland positional changes in the markings or tumour tissue, determined bythe movement detection device (7), in co-operation with the ion beamdeflecting device (1).